Effects of prostaglandin F_2α (PGF_2α) and flufenamic acid (FA) on termination of pregnancy were investigated in Wistar strain rats after day 17 of pregnancy. Results obtained are as follows.
1. Main urinary metabolite of endogenous PGF2a (PGF2a-MUM) and serum progesterone (P) levels were successively measured. PGF2a-MUM levels (ng/total 24-hour urine) increased from 594.5 on day 18-19 of pregnancy to 1242.5 on day 19-20 and to 1515.8 on day 21-22. P levels (ng/m/) decreased from 37.5 on day 19 to 16.7 on day 20 and 10.7 on day 21. Parturition cccured in two cases out of ten on day 21, seven on day 22 and one on day 23.
2. When FA was subcutaneously administered every day from day 19 of pregnancy until partu-rition, the decrease of serum P level (ng/ml) was delayed compared with control, showing 33.1 on day 20 and 19.4 on day 21, and parturition was also evidently prolonged in four cases out of eleven occurring on day 22, five on day 23 and one on day 24.
3. When the total dose of 0.5-1.0 mg/kg of exogenous PGF_2α were administered intramuscularly, induction of parturition was clearly recognized and this effect was observed 1-2 days after adminis-tration. Parturition-inducing effect of PGF_2α was not inhibited with FA, but was inhibited with P.
4. The fall of P level and elevation of intra-uterine pressure were recognized with exogenous PGF_2α. It required 48 hours to decrease to the extent of P level at near parturition, though the uterine contractile effect lasted only 40-60 minutes. Repeated administration of PGF_2α, at the dose causing no uterine contraction, also induced parturition. These results suggest that the increase of endogenous PGF_2α and the resultant luteolytic effect play important roles in spontaneous parturition in rats. It was considered that the luteolytic factor also largely accounts for the mechanism of parturition-inducing effect of exogenous PGF_2α.

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Hypophysectomized adult rats were injected daily with (1) testosterone propionate (TP, 1, 600 or 100μg), (2) TP (100μg) and cyproterone acetate (3) NIH-ICSH-S18 (9, 3μg), (4) NIH-FSH-S9 (300, 150, 100μg), (5) NIH-FSH (300μg), rabbit ICSH-antiserum (3ml) and CA (20mg), (6) PMSG(8 or 1 IU), (7) PMSG (1 lU) and CA (10mg) for15days, or (8) testosterone depot (testosteronepro-pionate, testosterone phenylpropionate, testosterone isocaproate, and testosterone decanoate; 2mg) for a long time (30, 151, and 313 days) beginning with the next day of hypophysectomy. They were examined for the effects of these hormones on the stage of spermiogenesis by counting germ cells in stages V, VII and XII of the cycle of the seminiferous epithelium.
1.The counts of spermatocytes and spermatids in rats administered with 1, 600μg of TP or 8 lU of PMSG were close to those in normal intact controls.
2. Spermatocytes in the transitional stage from zygotene to pachytene ands permatid in the acrosomic stage and maturation phases decreased in number in rats injected with a small dose of TP or ICSH.
3. A marked decrease was observed in the number of spermatocytes in the transitional stage from zygotene to pachytene in rats of fourdifferent groups which were administerd with FSH (100 or 150μg) or TP (100μg) alone, simultaneously with PMSG and CA, or simultaneously with FSH, rabbit ICSH-antiserum, and CA respectively. There were no or only a few cap-phase spermatids which were in the process of maturation to step 8 of the acrosomic phase.
4. Many spermatids in every step of the cap-phase of spermiogenesis were observed in rats in-jected with 300μg of FSH alone. In these rats, however, the development of spermatids was disturbed remarkably in the acrosomic phase.
5. The testes decreased in weight in proportion to the prolongation of the period of injection with testosterone. The testicular weight measured on the 313th day after the beginning of injection was almost the same as that in the hypophysectomized contro1. In rats on the 313th day, germ cells of every stage were reduced in number and especially spermatids in and after the acrosomic phase decreased remarkably in number.
6. Testosterone might play a leading role in the maintenance of spermatocytes in the transitional stage from zygotene to pachytene and in the process of metamorphosis in and after step 8 of spermio-genesis. It was observed that FSH itself had no effect on hypophysectomized adult rats. It was suggested that the action of testosterone itself might be insuffcient to maintain spermatogenesis for a long time and that the synergistic action of FSH might be necessary for testosterone to continue its action in such case.

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Meiotic arresting substance (MAS) was separated from cell surface of porcine granulosa cells and physicochemical characteristics of this substance was investigated.
Molecular weight of MAS was estimated to be 1, 450 to 3, 000 by gel filtration method using (Pro-Pro-Gly)₁₀ and Bacitracin. MAS was insoluble in acetone and ether, and was not dialyzed with cellulose tube (VT 801). Colorations of MAS by ninhydrine, phenol and biuret reactions were very strong, and photometric analysis of MAS dissolved in distilled water showed a peculiar absorption maximum near 260 mμ. Activity of MAS disappeared when digested by pronase, but did not disappear when treated by heat (100°C, 15 min.). Heparin, chondroitin sulfate and hyaluronic acid did not possess the meiotic arresting activity.
From these results, it is estimated that MAS is a peptide.

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Three androgen levels in the blood plasma of male dogs, following an intramuscular injection of hexestrol dicaprylate (H₈) were assayed and the state of spermatogenesis was examined in four of them. Sixteen male dogs were injected with a single dose of 0.5 mg/kg of H₈, and 4-androstenedione (A), testosterone (T), and 5α-dihydrotestosterone (DHT) in peripheral and/or spermatic vein plasma were measured by radioimmunoassay technics.
The results obtained were summarized as follows.
1. The 3 androgen levels in both peripheral and spermatic vein plasma of 12 dogs showed prompt, rapid decrease following the injection of H₈, and each decrease of peripheral plasma level of A, T, and DHT showed parallel to that in spermatic vein plasma.
2. After administration of H8, at least up to the 2 months period, each plasma level of these 3 androgens was kept very low, and spermatogenesis was not observed in this duration in all of 4 dogs examined. Whereas, between the 70th and 150th day, these androgen levels elevated sharply to attain the peaks, which were higher than the levels at each pre-injection time. Recovery of sperma-togenetic function was observed in each dog around the peak of blood androgen level.
These findings suggest that injected H8 influenced to inhibit spermatogenesis by interfering with androgen production in the interstitial tissue of testis in the male dogs.

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The follicular development and oocyte maturation were examined during the period of ovulation in immature rats pretreated with PMS. Immature female Wistar rats 2426 days of age were given PMS (3 i. u.) at 10:00 h. Animals were killed at various times after treatment with PMS (Table 1), and ovaries were prepared for serial sections at 10 μ and stained with hematoxylin-eosin. Two diameters of follicles were measured in the section in which the nucleolus of the oocyte was found. All the follicles over 300μ of the diameter were recorded. The oocytes in maturation divisions were classified according to Odor's category. Numbers of the large follicles over 500 μ increased 48 hrs to 60 hrs after PMS injection.
Number of the large follicles decreased slightly 62 h and markedly 72 h, when small follicles (300499 μ) developed again. The maturation division (the breakdown of germinal vesicles) started 55 h after PMS, one hour after the beginning of the LH surge. The timing of each stages of the maturation division during the period of ovulation in immature rats pretreated with PMS occurred in the same relation to that of adult cyclic rats.

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The present investigation was conducted to observe the histopathological characteristics of the genital organs in boars infected with porcine parvovirus (PPV).
The virus used was the 90 HS strain which had been isoloated from the brain tissue of stillborn piglets and undergone 8 passages in porcine embryo kidney established cell cultures. Three boars of miniature swine 5 months old which had been ascertained to be negative for antibody against PPV were inoculated subcutaneously with 2 ml, orally with 60 ml, and intratesticuraly with 1 ml of viral material of 10^5.5 TCID₅₀/ml, respectively.
No clinical symptoms were observed distinctly after inoculation, No remarkable changes were revealed found histopathologically in the genital organs. It was noticed, however, that spermatoge-nesis was disturbed in some of the seminiferous tubules. Mild inflammatory changes were found in the interstitial tissue of the epididymides, the seminal vesicles and the spermatic cord.
These results suggest that an abonrmal production of semen may occur in the boar when the infection of PPV is complicated with some disorder which can disturb spermatogenesis in this animal.

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Survival of rabbit blastocysts after various manipulation in uitro was studied.
1. Intact blastocysts maintained in uitro at 37°C, 5% 0₂ for 6 hr in calf serum were trans-ferred under several conditions. Synchronization between donor and recipient (5 day: donor-5 day: recipient) and induction of pseudopregnancy with a vasectomized male resulted in the highest survival rate (73%).
2. Day 5 blastocysts were pricked with a fine needle in Hams F₁₂+10% calf serum. Sixteen out of 22 blastocysts were re-expanded during culture. The treated blastocysts were transferred to the synchronized recipients (5D-5R) with high implantation rate (4475%) and living fetuses were obtained from the does previously mating with vasectomized males.
3. Some of trophoblastic cells from day 5 blastocysts were cut off with a sissor-tips after holing into the blastocyst coverings. About 66% of the manipulated blastocyst were re-expanded during culture in vitro at 37°C, 5% CO₂ for 6 hr following asynchronous transfer of their blastocy-sts and 49% (46/96) were implanted and seven fetuses were obtained.

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The effective dosage of intramuscular injection of PGF_2α and the effectiveness of intramuscular injection with PGF_2α followed by additional HCG on the synchronization of estrus and ovulation were investigated in the cow.
1. In the Exp. 1, 4 cows were injected intramuscularly (IM) with 1 of 3 doses of PGF_2α (10, 15 or 20 mg) during the luteal phase of the estrous cycle. Out of 4 cows in each group, 2 cows were given 2, 000 IU of HCG IM 42 hr later (HCG-42) and the other 2 cows 72 hr later (HCG-72), respec-tively after the PGF_2α injection. The number of cows showed sexual behavior after the treatment was smaller in HCG-42 (2 of 6 cows) than in HCG-72 (4 of 6 cows). The time intervals from the injection of HCG to ovulation ranged from 33 to 37 hr and 16 to 38 hr in HCG-42 and HCG-72, respec-tively. Blood progesterone level during the period of 24 hr after the PGF_2α injection in the cows given 20 mg of PGF_2α decreased dramatically, compared with those in the cows given 10 mg and 15 mg of PGF2a. In the cows given 15 mg of PGF_2α, blood progesterone level fell gradually by 48 hr after the PGF_2α injection and thereafter the pattern and the concentration of the blood progesterone were coincided with those in the cows given 20 mg of PGF_2a. In the cows given 10 mg of PGF_2α, blood progesterone level decreased slowly and had maintained as much level at 24 hr after the PGF_2α in-jection during the period of 6072 hr after the PGF_2α injection.
2. In the Exp. 2, 89 grazing Holstein cows, which were considered to be on 5 days or more after ovulation, were divided into four groups; i. e. Group A (26 cows) and Group B (19 cows) received the injection of PGF_2α plus 2, 000 IU of HCG IM, Group C (25 cows) and Group D (19 cows) received the injection of PGF_2α IM alone. The dosage of PGF_2α injected IM were 15 mg in Groups A and C, and 20 mg in Groups B and D. The time intervals from the PGF_2α injection to the injection of HCG in Groups A and B were 60 hr and 7374 hr, respectively. In Groups C and D, the occurrence of estrus after the PGF_2α injection was found to be synchronized effectively. In Groups A and B, however, the percentage of the cows in estrus by 96 hr after the PGF_2α injection was some-what low, but ovulation could be synchronized effectively, as compared to those in Groups C and D. There was no marked differences between Groups A and C, Groups B and D in the conception rates at the synchronized estrus.
From these results, it was concluded that the effective dosage of PGF_2α for regressing the corpus luteum rapidly and completely in the cow is about 15 mg or more, and the most efficient time interval from the injection of PGF_2α to the additional injection of HCG for the synchronization of estrus and ovulation may be between 42 hr and 72 hr, viz. 60 hr.

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